Display device, electronic apparatus and method of manufacturing display device

ABSTRACT

The invention provides a display device which improves the shape of the contact region while increasing yield and reducing product cost. A contact region is a region between signal lines, and is a region following a scan line so as to include either a part of or an entire of the pixel electrode edge region following the scan line connected to the switching element. The pixel electrode is connected to the source electrode in this region. The contact hole may be rectangular, and a plurality of contact holes may be provided. Also, if C X  is the parasitic capacitance between the pixel electrode and the source electrode when a bad contact exists between said pixel electrode, C 0MAX  is the maximum value of the pixel capacitance held by the pixel electrode when said bad contact does not exist, V LCMIN  is the voltage when the transmissivity at a pixel position is a minimum, and V LCMAX  is the voltage when the transmissivity is a maximum, a capacitance ratio RA C1  is set such that the following relationship is established: RA C1  =C X  /C 0MAX  &gt;V LCMAX  /(V LCMIN  -V LCMAX ). The invention thereby apparently eliminates a pixel defect of a bad contact.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device that uses a liquidcrystal display element, as well as a method of manufacturing anelectronic apparatus and display device which uses such a liquid crystaldisplay element.

2. Description of Related Art

Recently, it has become desirable to reduce the cost of liquid crystaldevices used for personal computers. Therefore, planning for theincreased manufacturing yield resulting from this cost reduction hasbecome an important technological issue. Preventing the panel pixeldefects ("dot defects") and shortening the manufacturing process arealso effective to increase manufacturing yield.

For example, Japanese Laid-Open Patent No. 4-155316 discloses a methodof manufacturing a liquid crystal device. However, in this conventionalmethod, the source electrode and the pixel electrode are on the samelayer, and a protective insulation film is not interposed therebetween.Therefore, the problem arises that pixel defects tend to be generateddue to shorts between the source electrode and the pixel electrode. Thegeneration of pixel defects decreases yield and increases product cost.

In Japanese Laid-Open Patent No. 3-1648, the source electrode and thepixel electrode are not on the same layer, and a protective insulationfilm is interposed between them. The source electrode and the pixelelectrode is connected through a contact hole. Therefore, in the priorart, any pixel defect due to shorts between the source electrode and thepixel electrode may not be easily generated. However, in the prior art,since a protective insulation is formed between the source electrode andthe pixel electrode, it is necessary to form a contact hole connectingthe source electrode and the pixel electrode, which increases the numberof process steps. Furthermore, if the quality of the contact hole ispoor, a pixel gap is formed, which decreases yield and increases productcost.

Thus, the conventional methods described above do not solve thetechnological problems such as increasing yield and reducing productcost.

DISCLOSURE OF INVENTION

An object of the invention is to solve the technological problemsdescribed above, and improve the contact region between the sourceelectrode and the pixel electrode. Therefore, it is an object of theinvention to provide a display device, an electronic apparatus and amethod of manufacturing an electronic apparatus and display device toincrease yield and reduce product cost.

In order to solve the above problems, the present invention relates to adisplay device including a pixel electrode for driving the displayelement and a switching element connected to the pixel electrode througha source electrode. A capacitance ratio RA_(C1) is set such that thefollowing relationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX)

wherein:

C_(X) is the parasitic capacitance between the pixel electrode and thesource electrode when a bad contact exists between the pixel electrode;

C_(0MAX) is the maximum value of the pixel capacitance held by the pixelelectrode when said the contact does not exist;

V_(LCMIN) is the voltage when the transmissivity at the pixel positionis a minimum; and

V_(LCMAX) is the voltage when the transmissivity is a maximum.

In accordance with the invention, when a parasitic capacitance C_(X) hasoccurred because of a bad contact, for example, in a normally-whitedisplay device, the pixel defects can be changed into a display toneshift, and it becomes possible to eliminate the pixel defectsapparently. For example, the voltage of the pixel where thetransmissivity is minimum T_(MIN) "black display pixel" can be made tobe greater than the voltage V_(LCMAX) during maximum transmissivity.Consequently, this pixel becomes gray rather than white. If the displayis gray, the invention makes it possible to eliminate the pixel defectsapparently.

The capacitance ratio can be set by controlling various parameters, suchas the overlapping surface area between the source electrode and thepixel electrode, the thickness of the insulating film, the materialused, etc. When controlling the overlapping surface area, the surfacearea of the contact region at the edge region of the pixel electrode maybe controlled. A storage capacitor may be included for the pixelcapacitance of the invention or, alternatively, it may not be included.

In accordance with the invention, the capacitance ratio RA_(C1) may beset such that:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMIN -V.sub.LCHL)

wherein:

V_(LCHL) is the voltage when the transmissivity in said pixel positionbecomes about 50% of the maximum transmissivity.

As a result, the transmissivity of a black display pixel, for example,can be made to be less than or equal to T_(HL), which is approximately50% of T_(MAX). If the transmissivity is less than or equal to T_(HL),the human eye detects almost no distinction from a black display.Consequently, the distinction becomes unnoticeable in the display to thehuman eye if great attention is not paid.

The pixel capacitance C₀ may change depending upon the voltage printedto the display element, for example, within the range C_(0MIN)-C_(0MAX). In this case, instead of the above equation, the capacitanceRA_(C2) may be set such that:

    RA.sub.C2 =C.sub.X /C.sub.0MIN >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).

Also, in a normally-black display device, the above relationships changeas shown below. Specifically, the capacitance is set such that:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMAX -V.sub.LCMIN);

or

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMAX -V.sub.LCHL);

or

    RA.sub.C2 =C.sub.X /C.sub.0MIN >V.sub.LCMIN /(V.sub.LCMAX -V.sub.LCMIN).

Thus, in a normally-black display device, the yield is increased and theproduct cost is reduced by preventing bad contacts.

The invention is also a display device having a pixel electrode fordriving the display element and a switching element connected to thepixel electrode by a source electrode. This invention includes a contactregion which is provided between a signal line connected to theswitching element and another signal line adjacent to the signal lineconnected to the switching element so as to include a part or an entireof the pixel electrode edge region along the scan line connected to theswitching element. Thereby the pixel electrode is connected to thesource electrode in the contact region.

In accordance with the invention, a contact region is provided in a wideregion included in a portion of or the entire pixel electrode edgeregion, therefore bad contacts are drastically reduced, which increasesyield and reduces product cost. Moreover, this pixel electrode edgeregion is at the edge of the pixel electrode and extends in a directionfollowing the scan line. The pixel electrode edge region can be coveredeasily by a black matrix and so on. Consequently, the invention reducesbad contacts from occurring without substantially sacrificing aperture,etc.

In accordance with the invention, the contact region does not have to beprovided across the entire pixel electrode edge region. The contactregion may be provided in a portion, for example half, of the pixelelectrode edge region. It is desirable that the size of the contactregion provided in the pixel electrode edge region be determined basedon, for example as described above, the parasitic capacitance thatoccurs when a bad contact is generated, the pixel capacitance held bythe pixel electrode, the voltage during minimum transmissivity andduring maximum transmissivity, and other characteristics. In accordancewith the invention, a portion of the contact region can be in a regionoutside of the pixel electrode edge region.

In accordance with the invention, the contact region may include arectangular contact hole, the long side of which follows the scan line.The pixel electrode and the source electrode can be connected by therectangular contact hole. The contact region can include multiplecontact holes. The pixel electrode can be connected to the sourceelectrode by the contact holes. A contact region of the desired surfacearea can be provided efficiently for the pixel electrode edge region bymaking a rectangular contact hole. Also, when multiple contact holes areprovided, it is desirable that the number of contact holes in thedirection following the scan line be greater than the number of contactholes in the direction following the signal line.

Also, in accordance with the invention, it is desirable that a blackmatrix region be provided to cover a portion of or the entire contactregion. For example, when the source electrode is formed of anon-transparent material, the existence of the contact region becomes afactor in the reduction of aperture. The existence of the black matrixregion provided for improving contrast becomes a factor in the reductionof aperture. Thus, by overlapping the contact region and the blackmatrix region, it becomes possible to reduce bad contacts and increasecontrast, while minimizing the reduction of aperture. The black matrixregion can be provided on the side of the opposing substrate or on theside of the switching element.

The method of manufacturing the display device in accordance with theinvention can include forming the source electrode, forming a giveninsulation film above the source electrode, forming contact region forconnecting at least the electrode and the pixel electrode, and formingthe pixel electrode. Also, in the contact region formation process, itis desirable that the contact region for connecting an electrode formedof the same material as the gate electrode of the switching element anda given electrode be formed concurrently with the formation of thecontact region for connecting the source electrode and the pixelelectrode. As a result, the contact region can be formed between thesource electrode and the pixel electrode at the same time as theformation of the contact region and "pad open," for example, whenforming a protection diode, and it becomes possible to plan for thereduction of the number of processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a planar structure in accordance with Embodiment 1 of theinvention.

FIG. 1B is a cross sectional view of P-Q portion of the planar structureof FIG. 1A.

FIG. 2A and FIG. 2B show a planar structure in accordance withEmbodiment 1 and a sectional view of Q-B portion of another embodiment(which is different in a method of forming a holding capacitance).

FIG. 3 shows another planar structure in accordance with Embodiment 1 ofthe invention.

FIG. 4 shows another planar structure in accordance with Embodiment 1 ofthe invention.

FIG. 5 shows another planar structure in accordance with Embodiment 1 ofthe invention.

FIG. 6 shows the relationship of the black matrix.

FIGS. 7A-7F are sectional views showing a method of manufacturing aplanar structure in accordance with Embodiment 1 of the invention.

FIGS. 8A-8G are sectional views showing another method of manufacturinga planar structure.

FIGS. 9A-9C show a protection diode.

FIGS. 10A and 10B are circuit diagrams in accordance with Embodiment 2of the invention.

FIGS. 11A and 11B show the relationship between the voltage V_(LC) andthe transmissivity T when normally-white and normally-black.

FIG. 12 shows a method of setting the capacitance ratio.

FIG. 13 shows a method of setting the capacitance ratio.

FIG. 14 shows an electronic apparatus in accordance with Embodiment 3 ofthe invention.

FIG. 15 shows an electronic apparatus which is a projector.

FIG. 16 shows an electronic apparatus which is a personal computer.

FIG. 17 shows an electronic apparatus which is a pager.

FIG. 18 shows a method of installation using TCP.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiment 1

Embodiment 1 of the invention relates to improving the shape, size andthe other characteristics of the contact hole. FIG. 1A shows a planarstructure in accordance with Embodiment 1 of the invention, and FIG. 1Bis a cross-sectional view of P-Q portion of FIG. 1A.

As shown in FIGS. 1A and 1B, the liquid crystal device of Embodiment 1of the invention includes a pixel electrode 10 formed of ITO or similarmaterial, and a thin film transistor 30, i.e., a switching element("TFT") connected to the pixel electrode 10 by a source electrode 40.These elements drive a liquid crystal element 76 ("display element")interposed between these elements and the opposing substrate 66.

TFT 30 includes at least a gate electrode 32, a drain electrode 34, asource electrode 40, an intrinsic silicon film 70 not doped withimpurities, and n-type silicon films 72 and 73 ("ohmic films"). Pixelelectrode 10 is connected to source electrode 40 by a contact hole 52inside a contact region 50. Gate electrode 32 and drain electrode 34 areconnected to a scan line 20 and a signal line 22, respectively. Amatrix-type liquid crystal display device is formed by placing multiplescan lines 20 and signal lines 22 crossing each other in a matrixpattern, and connecting TFT 30 to scan line 20 and signal line 22.

In accordance with the embodiment shown in FIG. 1B, a protectiveinsulation film 60 ("passivation") is formed as an interlayer insulationfilm between source electrode 40 and pixel electrode 10. Also, a storagecapacitor ("storage condenser") C_(ST) is formed by making thisinsulation film 60 and gate insulation film 49 as an dielectricsubstance, pixel electrode 10 as an upper electrode, and thefront-column scan line 21 as the lower electrode. However, the storagecapacitors formed by subsequent columns of scan lines (not shown) withpixel electrodes is not explained or shown for expediency. Also, aliquid crystal capacitor ("liquid crystal condenser") C_(LC) is formedby making liquid crystal element ("liquid crystal layer") 76 as andielectric substance, opposing electrode 66 as the upper electrode, andpixel electrode 10 as the lower electrode. Pixel electrode 10 may bedivided into sub-pixel electrodes so as to form a control condenserbetween given control electrodes.

Numerous methods can be considered for configuring the storagecapacitor. An example of one such method is shown in FIGS. 2A-2B. InFIGS. 2A-2B, pixel electrode 10 is connected to electrode 15 via contacthole 13, and storage capacitor C_(ST) is formed between this electrode15 and scan line 21. Here, electrode 15 is formed of the same material(same process) as source electrode 40, having a smaller side edgecompared with ITO, and similar materials, being a material of pixelelectrode 10. Consequently, it becomes possible to reduce themanufacturing uniformity of the storage capacitor by forming oneelectrode of the storage capacitor C_(ST) of electrode 15.

The main characteristic of this embodiment is that contact region 50 isprovided in a region between signal line 22 connected to TFT 30 and asignal line 23 adjacent to signal line 22, and so as to include either aportion of or the entire electrode edge region being a region followinga scan line 30 connected to TFT 30. Forming contact region 50 in thismanner reduces the number of bad contacts and makes it possible to planfor the improvement of yield and the reduction of product cost.

Contact hole 52 in contact region 50 can be formed into numerous shapes.For example, it may be rectangular, wherein the long sides follow thescan line 20 as shown in FIG. 1A. Alternatively, the region may includea plurality of contact holes 52a-52i as shown in FIG. 3.

Also, a contact region 50 does not have to be provided across the entireregion of the above-mentioned pixel electrode edge region. However, inthe case of a rectangular contact hole, for example, it is desirable toprovide the contact hole 50 across at least half of the pixel electrodeedge region. When a plurality of contact holes are provided, it isdesirable to provide two or more contact holes arrayed in the directionfollowing the scan line. Also, as explained below regarding Embodiment2, it is desirable that the surface area of the contact region bedetermined based on the parasitic capacitance C_(X) occurring during theformation of a bad contact, the pixel capacitance C₀ held by the pixelelectrode, the voltage V_(LCMIN) and V_(LCMAX) during minimumtransmissivity and during maximum transmissivity.

Also, contact region 40 may include the pixel electrode edge region. Asshown in FIG. 4, for example, a portion of contact region 50 can be in aregion outside the pixel electrode edge region.

Furthermore, the position of placement of TFT 30 is optional. Forexample, TFT 30 may be placed in a position as shown in FIG. 5. In FIG.5, scan line 20 is below intrinsic silicon film 70 and becomes a gateelectrode. Also, in the case of FIG. 5 contact region 50 is provided inthe entire region of the pixel electrode edge region.

In accordance with this embodiment, the formation of bad contacts can bereduced substantially without sacrificing aperture, as shown in FIG. 6.A liquid crystal display device usually is provided with alight-shielding layer, i.e., a black matrix. A color liquid crystaldisplay device is provided with a color filter on top of this.

In order to ensurely prevent light leakage, black matrix 63 must beprovided such that it overlaps inside pixel electrode 10, as shown inFIG. 6. In FIG. 6, for example, the value of that overlap is 7 μm. Whenblack matrix 63 is provided on the opposing substrate, for example,because the combined spatial allowance for the opposing substrate andthe TFT-side substrate and the combined spatial allowance for pixelelectrode 10 itself must be considered, this overlap value becomesrather large. A certain overlap value becomes necessary even when blackmatrix 63 is provided on the TFT-side substrate. When the size ofcontact hole 52 is 5 μm, and the overlap of source electrode 40 inrelation to contact hole 52 is 2 μm, the edge of black matrix 63 and theedge of contact hole 52 substantially correspond to each other, as shownin FIG. 6. When source electrode 40 is formed of a non-transparentmaterial, the section of source electrode 40 does not contribute to thedisplay in a transmissive liquid crystal display device. Nevertheless,because the positional relationships of contact region 50 and blackmatrix 63 are as shown in FIG. 6, the region that does not contribute tothe display being newly produced by the formation of contact region 50becomes extremely narrow, e.g., 2 μm wide. In other words, in accordancewith this embodiment, it becomes possible to reduce effectively theformation of bad contacts substantially without sacrificing aperture byforming contact 50 in the region covered by black matrix 63.

Japanese Laid-Open Patent No. 4-155316 discloses a structure having aplurality of contact holes ("contact holes A") connecting pixelelectrodes and storage capacitance electrodes. Nevertheless, thesecontact holes A are similar to contact holes 13 of FIG. 2A, and arecompletely different from contact holes 52 of this embodiment, whichconnect pixel electrodes and source electrodes.

Also, Japanese Laid-Open Patent No. 4-155316 discloses providingmultiple contact holes A for the purpose of increasing redundancy, suchthat the storage capacitance increases minimally, even when a badcontact occurs. Also, the multiple contact holes A substantially do notinfluence the operation of the liquid crystal display device.Consequently, the actual number of contact holes A does not need to beas much as shown in Japanese Laid-Open Patent No. 4-155316.Alternatively, a bad contact occurring in contact hole 52 of FIG. 1A, islinked to bad operation as shown in FIGS. 10A-10B, as described below.In this embodiment, the surface area of contact holes 52 is large andthe number of holes is numerous in order to avoid such bad operation.Also, the embodiment is entirely different from the disclosure ofJapanese Laid-Open Patent No. 4-155316 in the purpose and background.

An example of the manufacturing process of a liquid crystal displaydevice of this embodiment is explained below using the cross-sectionalviews shown in FIGS. 7A-7F.

Details of Each Manufacturing Process

Process 1

Using photolithography technology on a glass substrate, i.e., non-alkalisubstrate 68 shown in FIG. 7A, a gate electrode 32 is formed which isabout 1300 angstrom thick Cr ("chrome"), for example, and an electrodes31 and 33 made of the same material as the gate electrode. Next, a gateinsulation film 49 made of a silicon nitride ("SiN_(X) ") film, or thelike, an intrinsic silicon film 70, and a n-type silicon film ("ohmiccontact layer") 71 are formed successively by plasma CVD. Next,intrinsic silicon film 70 which is not doped with impurities and n-typesilicon film ("ohmic contact layer") 71 are formed into islands usingphotoetching.

In this case, the thickness of gate insulation film 49 can be, forexample, about 3000 angstroms, the thickness of intrinsic silicon film70 can be, for example, about 3000 angstroms, and the thickness of ohmiccontact layer 71 can be, for example, about 500 angstroms.

The characteristic of this process is that the contact holes are notformed in relation to the gate insulation film.

Process 2

Next, a drain electrode 34 and source electrode 40 made of Cr ("chrome")extending 1300 angstroms are formed by sputtering and photoetching, forexample, as shown in FIG. 7B.

Process 3

Next, as shown in FIG. 7C, drain/source separation is performed("separation etching") by etching and eliminating the center of theohmic contact layer 71 using drain electrode 34 and source electrode 40as masks. In this case, the etching for patterning the drain electrodeand source electrode and the separation etching can be performedsuccessively in the same chamber of the same etching apparatus.

That is, drain electrode 34 and source electrode 40 are first etchedwith a Cl₂ system gas, and then the center of ohmic contact layer 71 isetched by switching the etching gas to a SF₆ system gas.

Process 4

Next, as shown in FIG. 7D, a protective insulation film 60 is formed,for example, by a plasma CVD. This protective insulation film 60 may be,for example, a silicon nitride film ("S_(i) N_(x) ") to the extent of2000 A.

Process 5

Next, as shown in FIG. 7E, a contact hole ("aperture") 59 is formed forconnecting an external terminal, i.e., bonding wire, outer lead of IC,or similar device, to a portion of protective insulation film 60. At thesame time, contact holes 52 and 58 are formed. Contact hole 52 connectssource electrode 40 and pixel electrode 10. Also, contact hole 59interconnects electrode 31 formed in the same process with the gateelectrode and the pixel electrode. This hole is necessary for forming aprotective diode, or similar device. Furthermore, contact hole 58 isnecessary for forming an external terminal or test terminal.

Contact holes 58 and 59 are formed by piercing the overlapping films ofgate insulation film 49 and protective insulation film 60. Contact hole52 is formed by piercing only protective insulation film 60.

When forming contact holes 58 and 59, electrodes 31 and 33 each operateas etching stoppers. Also, when forming contact hole 52, sourceelectrode 40 operates as an etching stopper.

Process 6

Next, as shown in FIG. 7F, pixel electrode 10 and electrode 11 areformed from ITO ("Indium Tin Oxide") by depositing an ITO film to athickness of as much as 500 angstroms, and etching it selectively. Theetching of the ITO is performed by wet etching using a mixture ofHcl/HNO₃ /H₂ O.

As described above, contact holes 58 and 59 are formed by piercing theoverlapping films of gate insulation film 49 and protective insulationfilm 60. Consequently, contact holes 58 and 59 define a deep contacthole equivalent to the thickness of two layers of insulation films.

However, because ITO has a high melting point, its step coverage isbetter than aluminum. Consequently, it does not create a bad connectioneven when extending through a deep contact hole. Other transparentelectrode materials having a high melting point, such as a metal oxide,can be used instead of ITO. For example, oxide films such as SNO_(X),ZNO_(X), and similar materials, can be used. In these cases, the stepcoverage can stand up to practical use.

A TFT manufactured in such a manner can be used as a switching elementof a pixel region in an active matrix substrate. Also, an electrode 11which is formed of ITO can become a pad for connecting an externalterminal, i.e., outer lead of IC, or similar device.

Characteristics of the Present Manufacturing Method

FIGS. 8A-8G show an alternative method of manufacturing a TFT. Thisalternative method was conceived by the present inventors in order tomake clear the characteristics of the TFT manufacturing method of thisembodiment.

FIG. 8A of the alternative example is the same as FIG. 7A. In FIGS.8A-8G, the same elements have the same reference numbers as in FIGS.7A-7F.

In the alternative example, contact holes K1 and K2 are formed beforedrain electrode 34 and source electrode 40 are formed, as shown in FIG.8B.

Also, electrodes 42 and 44 are formed along with drain electrode 34 andsource electrode 40, which are composed of the same material, as shownin FIG. 8C.

Next, pixel electrode 46 is formed with ITO, as shown in FIG. 8D.

Next, etching, i.e., separation etching, of the middle section of ohmiccontact layer 71 is performed, as shown in FIG. 8E.

Next, protective insulation film 48 is formed, as shown in FIG. 8F.

Finally, contact hole K3 is formed, as shown in FIG. 8G. Thus thesurface of electrode 44 is exposed, and a pad is formed for connectingan external connection terminal.

In accordance with the manufacturing method of the alternative example,an additional process for forming contact hole K3 in FIG. 8G is added tothe process that forms contact holes K1 and K2 in FIG. 8B. In total, twocontact hole formation processes are required.

Alternatively, in the manufacturing method of this embodiment, contactholes 52, 58, and 59 are formed in one batch as shown in FIG. 7E. Inother words, one contact hole formation process is sufficient bypatterning protective insulation film 60 on source electrode 40concurrently with the formation of contact holes by piercing theoverlapping films of protective insulation film 60 and gate insulationfilm 49. Consequently, the light exposure process is curtailed via oneprocess. Concomitant with this, a photoresist deposition process and itsetching process are obviated. Consequently, the method is shortened bythree processes. In other words, the manufacturing process issimplified.

Also, in accordance with the manufacturing process of this embodiment,patterning ("dry etching") of drain electrode 34 and source electrode 40shown in FIG. 7B and etching ("dry etching") of the center of ohmiccontact layer 71 shown in FIG. 7C are performed successively in the samechamber. In other words, consecutive etching is possible by switchingthe etching gas sequentially in the same chamber.

However, in the case of the alternative example, after patterning ("dryetching") of drain electrode 34 and source electrode 40 in FIG. 8C, wetetching of pixel electrode 46 which is made of ITO of FIG. 8D isperformed. Next, etching ("dry etching") of the center of ohmic contactlayer 71 of FIG. 8E is performed. Because ITO cannot be processed by dryetching, and can only be processed by wet etching, each etching processof FIGS. 8C-8E cannot be performed consecutively in one chamber.Consequently, the substrate must be handled in each process, and thework is troublesome.

Also, in the case of this embodiment, a protective insulation film 60must be placed between pixel electrode 10 and electrode 11 made of ITO,and drain electrode 34 and source electrode 40. Thus, electrodescomposed of ITO and electrodes composed of the same material as thedrain electrode and the source electrode assuredly can be separatedelectrically in the other regions (not shown) on the substrate.

However, in the alternative example, electrode 46 and drain electrode 34and source electrode 40 belong to the same layer, and a protectiveinsulation film cannot be placed between them. Consequently, if aextraneous material is present in another region (not shown) on thesubstrate, there is a concern that the electrodes composed of ITO andthe electrodes composed of the same material as the drain electrode andthe source electrode may short, despite the fact that they must beinsulated naturally. In other words, the device formed by themanufacturing method of this embodiment is highly reliable.

Also, in the alternative example, because electrode 46 composed of ITOis formed at a comparatively early stage as shown in FIG. 8D,contamination may occur in subsequent processing by indium ("In") andtin ("Sn"), which are constituents of ITO.

However, in the manufacturing method of this embodiment, becauseelectrode 10 and electrode 11, composed of ITO, are formed at the finalstage, there is no problem of contamination by tin ("Sn"), and similarmaterials, which are the constituents of ITO.

Thus, in accordance with the manufacturing method of this embodiment,the manufacturing processes can be reduced, and a highly reliable devicecan be manufactured.

Next, protective diodes used in this embodiment are shown in FIGS.9A-9C. As shown in FIG. 9A, protective diodes 200, 201, and 202 areprovided in order to protect the TFTs, and similar devices, connected toscan line 233 and signal line 234 and 236, from external staticelectricity. Also, as shown in FIG. 9A, protective diodes 200, 201 and202 are formed in the region of outside of display region 203. Morespecifically, protective diode 200 allows the static electricity addedto scan line 233 from pad 214 to escape to LC common line 204, andprotective diodes 201 and 202 allow the static electricity added tosignal lines 234 and 236 from pads 216 and 218 to escape to LC commonline 204. LC common line 204 is connected to an external driver IC inaddition to being connected to the opposing electrode via silver pointpads 206-209.

FIG. 9B is an example of an equivalent circuit drawing of protectivediodes 200-203. These protective diodes, as shown in FIG. 9B, includeTFTs 220 and 222 which have a gate electrode connected to a drainelectrode, and operate as elements having a non-linear impedance inrelation to the source/drain voltage, i.e., they have high impedancewhen low voltage is applied, and they have low impedance when highvoltage is applied.

FIG. 9C is an plane view (layout) of protective diode 200 in accordancewith this embodiment. The main characteristic of this protective diodeis that source electrode 240 of TFT 222 is connected to scan line 233via contact holes 252a,b, electrode 210, formed of the same material asthe pixel electrode, and contact holes 259a-b. Contact holes 252a-b areequivalent to contact hole 52 of FIG. 7F, electrode 210 corresponds topixel electrode 10, contact holes 259a-b correspond to contact hole 59,and scan electrode 233 corresponds to electrode 33. In short, in orderto form the protective diodes of this embodiment, it is necessary toconnect source electrode 240 and scan electrode 233.

In this embodiment as shown in FIG. 7A, a contact hole for gateinsulation film 49 is not formed in order to reduce the number offormation processes of the contact hole. Consequently, source electrode240 cannot be connected directly to scan line 233 via a contact hole inthe gate insulation film. Thus, in this embodiment, after the gateinsulation film and the protective insulation film are formed sourceelectrode 240 is connected to scan electrode 233 by simultaneouslyopening contact holes 252a-b and 259a-b, and by using electrode 210deposited thereafter.

Electrode 210 is formed of ITO, or similar device, which is the samematerial as the pixel electrode. Also, ITO is better in step coverage,and similar characteristics, compared with aluminum because it has ahigh melting point. In addition, because ITO is formed by reactionsputtering, or similar processes, the solid angle can be increasedsubstantially, and the step coverage can be made to be even better thanchrome, and similar materials. Consequently, if an ITO is used such asthe one of this embodiment, it is possible to make a good interelectrodeconnection even through a deep contact hole, such as when both the gateinsulation film and the protective insulation film are pierced.

Embodiment 2

Embodiment 2 eliminates a pixel defect apparently even when a badcontact has formed between source electrode and pixel electrode bychanging this into a bad tone shift, or similar characteristics.

First, the principles are explained using FIGS. 10A-10B. FIG. 10A is acircuit drawing of a liquid crystal display device when no bad contactsexist between source electrode 40 and pixel electrode 10. FIG. 10B is acircuit drawing when a bad contact does exist. When no bad contactsexist as shown in FIG. 10A, a liquid crystal capacitor C_(LC) and astorage capacitor C_(ST), having an opposing electrode ("LC commonline") as the other electrode, are connected to source electrode 40 andpixel electrode 10 of TFT 30. Alternatively, when a bad contact doesexist as shown in FIG. 10B, a given parasitic capacitance C_(X) isformed between source electrode 40 and pixel electrode 10. When such aparasitic capacitance C_(X) is formed, the voltage applied to the liquidcrystal, i.e., liquid crystal applied voltage is reduced from V_(LC) toV_(LC) *, and a pixel defect is caused by this, such as a white defectby a black display pixel turning to a white display.

The relationship between the voltage V_(LC) * and V_(LC) applied to theliquid crystal with a bad contact is:

    V.sub.LC *={C.sub.X /C.sub.0 (V.sub.LC *)+C.sub.X)}×V.sub.LC (1)

as is clearly shown in FIG. 10B.

Here, C₀ (V_(LC) *)=C_(LC) (V_(LC) *)+C_(ST), and C₀ (V_(LC) *) changesaccording to the value of V_(LC) *. In the case of a structure notproviding a storage capacitor, C₀ (V_(LC) *)=C_(LC) (V_(LC) *). Also,even when a storage capacitor is formed, there are many types of storagecapacitors. For example, a storage capacitor may be formed between pixelelectrode 10 or electrode 15 and the neighboring scan line 21, as shownin FIGS. 1A-2B, and a storage capacitor may be formed between pixelelectrode 10 and a given electrode for storage capacitance.

In this embodiment, the procedure described below is applied in order toprevent the generation of pixel defects due to the reduction of V_(LC)as shown in Equation (1). That is, first, if V_(LCMIN) is the voltagewhen the transmissivity in the pixel location is the minimumtransmissivity, V_(LCMAX) is the voltage when it is the maximumtransmissivity, C_(0MAX) is the maximum value of pixel capacitance C₀(in case of black display, or the like), and C_(0MIN) is the minimumvalue, the capacitance ratio RA_(C1) is set such that the followingrelationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX) (2)

As is clear from Equations (1) and (2), if the relationship of Equation(2) is established, the relationship: ##EQU1## is established. Forexample, FIG. 11A shows one example of the relationship between voltageV_(LC) and transmissivity T of a liquid crystal display device of anormally-white method. According to this embodiment, the voltage V_(LC1)(V_(LCMIN)) of the pixel, for example, where the transmissivity is theminimum transmissivity, that is, black display, changes to V_(LC1) *.This V_(LC1) * is greater than V_(LCMAX), as shown in FIG. 11A, andconsequently, this pixel does not become a white display, rather itbecomes a gray display. If it is a gray display, the human eyesubstantially does not notice it. As a result, according to thisembodiment, a pixel defect can be eliminated apparently. The above factis clear also from the fact that, when V_(LC) *=V_(LC1) * and V_(LC)=V_(LC1) =V_(LCMIN),

    V.sub.LC1 >V.sub.LCMAX.                                    (4)

However, as shown in FIG. 11A, even for a pixel not of black display,where the voltage is V_(LC2), the voltage V_(LC2) only changes toV_(LC2) *, and only the display tone is shifted. Consequently, a pixeldefect can be apparently eliminated even for such a pixel.

According to this embodiment, by setting the capacitance ratio RA_(C1)such that Equation (2) is satisfied, at least the pixels of a blackdisplay can be prevented from turning into a white display. Thus, when abad contact has formed, the condition whereby that pixel appears clearlyas a pixel defect is prevented. Nevertheless, in order to apparentlyeliminate this pixel defect, it is desirable to set the capacitanceratio RA_(C1) to be even larger. For example, if V_(LCHL) is the voltagewhen the transmissivity in the pixel location is approximately 50% ofthe maximum transmissivity T_(MAX), it is desirable to set thecapacitance ration RA_(C1) such that it becomes:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMIN -V.sub.LCHL). (5)

By setting in this manner, as is clear from Equation (1) and Equation(5): ##EQU2## Consequently, as is clear from Equation (6), according tothis invention, the transmissivity of a black pixel (V_(LC) =V_(LC1)=V_(LCMIN)) can be less than or equal to T_(HL), which is approximately50% of T_(MAX). If the transmissivity is less than or equal to T_(HL),the human eye sees almost no distinction from a black display.Consequently, the display is unnoticeable to the human eye if greatattention is not paid.

Furthermore, it is preferable to set the capacitance ratio such that thetransmissivity during a black display becomes less than or equal toapproximately 10% of T_(MAX). Thus, a display can be made whereby thepixel defect is substantially unnoticeable to the human eye.Nevertheless, there may be cases where the capacitance ratio cannot bemade so large from the relationships with the aperture, and the like. Insuch a case, the capacitance ratio may be set such that thetransmissivity during a black display becomes approximately 50%-90% ofT_(MAX). If the transmissivity is in the range of approximately 50%-90%of T_(MAX), the pixel defect is more easily noticed by the human eye,but an effect can be achieved such as correcting the pixel defect to atone shift.

If the relationship of Equation (2) is established, even though a badcontact occurs, and the voltage applied to a black display pixel (V_(LC)=V_(LC1) =V_(LCMIN)) is reduced to V_(LC1) *, the voltage V_(LC1) *assuredly can be made to be greater than V_(LCMAX), as is clear fromEquation (4).

However, in place of Equation (2), even when the capacitance ratioRA_(C2) is set such that the relationship:

    RA.sub.C2 =C.sub.X /C.sub.0MIN >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX) (7)

is established, a black display pixel can be prevented from becoming awhite display.

In other words, if Equation (7) is established,

    {C.sub.X /(C.sub.0MIN +C.sub.X)}×V.sub.LC >{V.sub.LCMAX /V.sub.LCMIN }×V.sub.LC                                          (8)

Meanwhile, the pixel capacitance C₀ (V_(LC) *) is a function of theabove-mentioned V_(LC) *, and because C₀ (V_(LC) *) is greater thanC_(0MIN) :

    {C.sub.X /(C.sub.0MIN +C.sub.X)}×V.sub.LC >{C.sub.X /C.sub.0 (V.sub.LC *)+C.sub.X)}×V.sub.LC                     (9)

Consequently, according to the value of the pixel capacitance C₀ (V_(LC)*), there are cases whereby:

    V.sub.LC *={C.sub.X /(C.sub.0 (V.sub.LC *)+C.sub.X)}×V.sub.LC >{V.sub.LCMAX /V.sub.LCMIN }×V.sub.LC               (10)

If Equation (10) is established, V_(LC) *=V_(LC1) *, and when V_(LC)=V_(LC1) =V_(LCMIN), the relationship:

    V.sub.LC1 *>V.sub.LCMAX                                    (11)

is established, and a black display pixel is prevented from becoming awhite display.

For example, since V_(LCMIN) =5V, V_(LCMAX) =1V, C_(0MAX) =140 fF (blackdisplay), and C_(0MIN) =80 fF (white display) when these values areinserted into Equation (2): ##EQU3## Consequently, if C_(X) is greaterthan 35 fF, a black display pixel can be assuredly prevented frombecoming a white display.

However, if the above values are inserted into Equation (7): ##EQU4##Thus, 30 fF is selected as the C_(X) that satisfies Equation (13). TheC_(X) is less than 35 fF and does not satisfy Equation (12). However,according to the value of C₀ (V_(LC) *) during reduction of voltageV_(LC) *, a black display pixel may be prevented from becoming a whitedisplay. That is, if the case is considered where the C₀ (V_(LC) *) of ablack display pixel is reduced from 140 fF to 90 fF due to the reductionof V_(LC) *, from Equation (1): ##EQU5## Consequently, the voltage of ablack display pixel may be reduced from V_(LC1) =V_(LC) =V_(LCMIN) =5Vto V_(LC1) *=V_(LC) *=1.25V. However, because the relationship V_(LC1)*=1.25V>V_(LCMAX) =1V is established, the black display pixel does notbecome a white display. Instead, it becomes a gray display. Thus,because there are cases when Equation (10) is established according tothe value of C₀ (V_(LC) *), even when setting the capacitance ratio suchthat Equation (7) is established, a black display pixel can be preventedfrom becoming a white display.

Examples using the normally-white method have been mainly discussedabove. However, in the case of a normally-black method as shown in FIG.11B, the relationships of Equations (2), (5), and (7) become:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMAX -V.sub.LCMIN) (15)

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMAX -V.sub.LCMIN) (16)

    RA.sub.C2 =C.sub.X /C.sub.0MIN >V.sub.LCMIN /(V.sub.LCMAX -V.sub.LCMIN) (17)

In a normally-black method as well, as shown in FIG. 11B, by the voltageof a white display pixel changing from V_(LC3) to V_(LC3) *, the pixelcan be made to be a gray display rather than a black display. Since thevoltage of non-white pixels changes from V_(LC4) to V_(LC4) *, a pixeldefect can be changed into a tone shift, and degradation of the displaycharacteristics can be prevented when a pixel defect exists.

Also, various methods of adjusting the capacitance ratios RA_(C1) andRA_(C2) can be considered. The first method is a method that adjusts theoverlap surface area, or the like, between source electrode 40 and pixelelectrode 10. That is, the capacitance ratio can be adjusted byadjusting the electrode surface area of the parasitic capacitor C_(X).In this case, it is desirable to form the contact region as explained inEmbodiment 1. That is, as explained in Embodiment 1, if the contact holeis rectangular, and the surface area of the contact region is larger,the formation of bad contacts can be reduced, and the capacitance ratiocan be greater. Therefore, as is clear from Equation (3), the decreaseof the voltage V_(LC) when a bad contact exists can be smaller.Consequently, combining Embodiments 1 and 2 provides a mutuallysynergetic effect, and separate effects not achievable individually byEmbodiments 1 and 2 can be achieved.

Also, the second method is a method of correcting the film thickness ofthe protective insulation film 60 interposed between source electrode 40and pixel electrode 10. That is, the capacitance ratios RA_(C1) andRA_(C2) can be corrected by correcting the interelectrode distance ofthe parasitic capacitor C_(X). This method, depending on therelationship with the aperture, and the like, is effective when theoverlap surface area, and the like, of source electrode 40 and pixelelectrode 10 cannot be adjusted so much. Various other methods ofadjusting the capacitance ratio can be adopted, such as changing thematerial quality of protective insulation film 60, and adjusting theliquid crystal capacitance C_(LC) and the storage capacitance C_(ST).

Lastly, examples of setting the capacitance ratio are shown in FIGS.12-13.

Here, the liquid crystal panel is a 13-inch SXGA display. As shown inFIGS. 12-13, the pitch of pixel electrodes 10 is 201 μm vertically and67 μm horizontally. Also, the distance between signal lines 22 and 23,and pixel electrodes 10, and the distance between scan lines 20 and 21,and pixel electrodes 10 are both 7 μm. Also, the widths of scan line 20and signal line 22 are both 10 μm. Thus, the size of pixel electrodes 10is 177 μm vertically and 43 μm horizontally. The liquid crystalcapacitance C_(LC) becomes:

C_(LC) =100 fF (black display)˜50 fF (white display) Also, the storagecapacitance C_(ST) becomes:

    C.sub.ST =25 fF.

Thus,

    C.sub.0 =125 fF (C.sub.0MAX)˜75 fF (C.sub.0MIN)

Also, the film thickness of the protective insulation film 60 that formsparasitic capacitor C_(X) is 2000 Angstrom, and the specific inductivecapacity is set to ε=6.5. Furthermore, in a liquid crystal as shown inFIG. 11A, generally the voltage during minimum transmissivity is suchthat T_(MIN) becomes approximately V_(LCMIN) =4.8V, for example, and thevoltage during maximum transmissivity T_(MAX) becomes approximatelyV_(LCMAX) =1.5V, for example.

In the case shown in FIG. 12, the size of contact 52 is smaller, i.e.,both horizontally and vertically, and the size of source electrode 40 is9 μm both horizontally and vertically. Consequently, the overlap surfacearea between pixel electrode 10 and source electrode 40 is 81 μm². Thus,the parasitic capacitance C_(X) and the capacitance ratio RA_(C1) are:##EQU6## Here, the voltage of the black display pixels is V_(LC)=V_(LC1) =V_(LCMIN) =4.8V. Consequently, when the voltage of the blackdisplay pixels has a bad contact, as shown in Equation (1): ##EQU7## InEquation (18), V_(LC) * to C₀ (V_(LC) *) are in a recursiverelationship. Thus, initially the V_(LC) * when C₀ (V_(LC) *)=C_(0MAX)=125 fF is sought. Doing thus: ##EQU8## In the above case, becauseV_(LC) =0.75V<V_(LCMAX) =1.5V, it is thought that the pixels form awhite display, and C₀ (V_(LC) *) is thought to be reduced to C_(0MIN)=75 fF. Thus, when C₀ (V_(LC) *)=C_(0MIN) =75 fF is inserted again intoEquation (18): ##EQU9## Because V_(LC) *=0.14V<V_(LCMAX) =1.5, as isclear from FIG. 11A, the black display pixels form a completely whitedisplay as expected, and the pixel defect is immediately recognizable tothe human eye. That is, if contact hole 52 is made into a shape as shownin FIG. 12, and the capacitance ratio is set to RA_(C1) =0.19, it isimpossible to eliminate the appearance of the pixel gap.

However, in the case shown in FIG. 13, contact hole 52 is shaped asshown in FIG. 4 of Embodiment 1, the total length is 50 μm, and thewidth is 5 μm. Also, because the overlap margin between source electrode40 and contact 52 is 2 μm, the overlap surface area between pixelelectrode 10 and source electrode 40 is 486 μm² (12×9+30×9).Consequently, the parasitic capacitance C_(X) and the capacitance ratioRA_(C1) in the case shown in FIG. 13 are: ##EQU10## Also, the voltage ofthe black display pixels when a bad contact has formed becomes:##EQU11## In the same manner as the described above, initially theV_(LC) * when C₀ (V_(LC) *)=C_(0MAX) =125 fF is sought. Doing thus:##EQU12## In the above case, because V_(LC) *=2.54V<V_(LCMAX) =1.5, itis thought that the black display pixels are intermediate between awhite display and a black display, and C₀ (V_(LC) *) is reduced to, forexample, 100 fF ((125+75)/2). Thus, when C₀ (V_(LC) *)=100 fF is againinserted into Equation (19): ##EQU13## Because V_(LC) *=2.80V>V_(LCMAX)=1.5V, as is clear from FIG. 11a, the black display pixels form a graydisplay, and the pixel defect is apparently eliminated. That is, thepixel defect can be shown as a tone shift, and the displaycharacteristics can be improved.

Because the above explanation is simplified, Equations (18) and (19) aresolved and V_(LC) * is sought by simple methods using a simplified C₀(V_(LC) *) . However, to perform a more reliable design, it is desirableto seek V_(LC) * more accurately by actually measuring the voltagedependencies of C₀ (V_(LC) *) and by numerical simulation, and similarprocesses.

Embodiment 3

Embodiment 3 relates to an electronic apparatus including a displaydevice as explained in Embodiments 1 and 2. FIG. 14 shows an example ofits structure. The electronic apparatus of FIG. 14 includes a displaydata output source 1000, a display data processing circuit 1002, a drivecircuit 1004, a liquid crystal panel 1006 which is one display device, aclock generation circuit 1008, and a power supply circuit 1010. Displaydata output source 100 includes ROM and RAM memory, a synchronizingcircuit, and similar device, and it outputs display data such as videosignals based on clock pulses from clock generation circuit 1008.Display data processing circuit 1002 outputs display data after havingprocessed the data based on clock pulses from clock generation circuit1008. This display data processing circuit 1002 can include suchcircuits as, for example, an amplifier/polarity-reversing circuit, aphase extension circuit, a rotation circuit, a gamma correction circuit,or a clamping circuit. Drive circuit 1004 includes a scan signal drivecircuit and a data signal drive circuit, and it drive liquid crystalpanel 1006. Power supply circuit 1010 supplies electrical power to eachof the above circuits.

Examples of an electronic apparatus of such configuration include theliquid crystal projector shown in FIG. 15, the multimedia personalcomputer (PC) and engineering workstation (EWS) shown in FIG. 16, thepager shown in FIG. 17, or a portable telephone, a word processor, atelevision, a viewfinder-type or direct sight-type video tape recorder,an electronic notebook, an electronic desktop computer, a car navigationapparatus, a POS terminal, and an apparatus having a touch panel.

The projector shown in FIG. 15 is a projection-type projector using atransmissive-type liquid crystal panel as a light valve. The projectorhas an optical system such as one which uses a three-prism method. Inprojector 1100 in FIG. 15, the projected light which emerges from whitelight source lamp unit 1102 is separated into the three primary colors,red, green, and blue (RGB) by a plurality of mirrors 1106 and twodichroic mirrors 1108. The light is led to three active matrix liquidcrystal panels 1110R, 1110G, and 1110B for displaying images of thevarious colors. Also, the light modulated by the various liquid crystalpanels 1110R, 1110G, and 1110B is introduced from three directions intoa dichroic prism 1112. In dichroic prism 1112, the red R and blue Blight is bent 90°, the green G light proceeds directly, the images ofeach color are composed, and the color image is projected onto a screen,or similar device, passing through a projection lens 1114.

The personal computer 1200 shown in FIG. 16 has a main body 1204equipped with a keyboard 1202, and a liquid crystal display screen 1206.

A metallic frame 1302, a liquid crystal display substrate 1304, a lightguide equipped with a backlight 1306a, a circuit board 1308, a first andsecond shielding plate 1310 and 1312, two flexible conductive members1314 and 1316, and a film carrier tape 1318 are provided in the interiorof the pager 1300 shown in FIG. 17. The two flexible conductive members1314 and 1316, and film carrier tape 1318 connect liquid crystal displaysubstrate 1304 with circuit board 1308.

Here, liquid crystal display substrate 1304 has liquid crystal filledbetween two transparent substrates 1304a and 1304b. At least a bitmatrix-type liquid crystal display panel is configured by thisapparatus. Additionally, the drive circuit 1004 shown in FIG. 14 or adisplay data processing circuit 1002 can be formed on one of thetransparent substrates. The circuits that are not mounted on liquidcrystal display substrate 1304 can be connected to an externallyattached liquid crystal display substrate, and in the case of FIG. 17,to circuit board 1308.

FIG. 17 shows the structure of a pager. A circuit board 1308 is requiredin addition to the liquid crystal substrate 1304. However, if the liquidcrystal display device is used as a component for an electronicapparatus, when a drive circuit is mounted on a transparent substrate,the minimum unit of that liquid crystal display device is liquid crystaldisplay substrate 1304. Alternatively, one having liquid crystal displaysubstrate 1304 fixed to a metallic frame 1302 can be used as a liquidcrystal display device as a component for an electronic apparatus.Furthermore, in the case of a backlight-type, the liquid crystal displaydevice can be manufactured by assembling liquid crystal displaysubstrate 1304 and light guide 1306 equipped with backlight 1306a insidemetallic frame 1302. Instead of these, by connecting a TCP (Tape CarrierPackage) having an IC chip 1324 packaged on a polyamide tape 1322 formedof a metallic conductive film on one of the two transparent substrates1304a and 1304b composing liquid crystal display substrate 1304, asshown in FIG. 18, it can be used as a liquid crystal display device asone component for an electronic apparatus.

The invention is not limited to Embodiments 1-3 described above, andvarious modifications are encompassed within the scope of thisinvention.

For example, the structure of the switching element is not limited tothose explained in the above embodiments, and various structures can beused such as, for example, an entirely backward configuration on a thinamorphous silicon thin film transistor, or the forward configuration, ora planar, forward configuration on a thin polycrystalline silicon film.

Also the method of manufacturing the liquid crystal display device isnot limited to that explained in the above embodiments, and variousmodifications are possible, such as modifying the order of theprocesses, or adding other processes.

Also, the shape of the contact region is not limited to that explainedin the above embodiments, and equivalent shapes can be used in thisinvention.

Also, the relationship equations of the capacitance ratio are notlimited to those explained in the above described embodiments, andequivalent equations can be used in this invention.

Also, the above embodiments discuss cases wherein the appearance of apixel gap is eliminated by setting the capacitance ratio. However,methods of setting parameters other than the capacitance ratio may beincluded in the range of equivalence to this invention as long assubstantially the same operation and effect are achieved.

I claim:
 1. A display device, comprising:a pixel electrode for drivingthe display device; and a switching element connected to said pixelelectrode via a source electrode; wherein, if C_(X) is the parasiticcapacitance between the pixel electrode and the source electrode when abad contact exists between said pixel electrode and the sourceelectrode, C_(0MAX) is the maximum value of the pixel capacitance heldby the pixel electrode when said bad contact does not exist, V_(LCMIN)is the voltage when the transmissivity at a pixel position is a minimum,and V_(LCMAX) is the voltage when the transmissivity is a maximum, acapacitance ratio RA_(C1) is set such that the following relationship isestablished:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).


2. A display device according to claim 1, wherein, if V_(LCHL) is thevoltage when the transmissivity in said pixel position is approximately50% of the maximum transmissivity, the capacitance ratio RA_(C1) is setsuch that:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMIN -V.sub.LCHL).


3. A display device, comprising:a pixel electrode for driving thedisplay device; and a switching element connected to said pixelelectrode via a source electrode; wherein, if C_(X) is the parasiticcapacitance between the pixel electrode and the source electrode when abad contact exists between said pixel electrode and the sourceelectrode, C_(0MAX) is the maximum value of the pixel capacitance heldby the pixel electrode when said bad contact does not exist, V_(LCMIN)is the voltage when the transmissivity at a pixel position is a minimum,and V_(LCMAX) is the voltage when the transmissivity is a maximum, acapacitance ratio RA_(C2) is set such that the following relationship isestablished:

    RA.sub.C2 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).


4. A display device, comprising:a pixel electrode for driving thedisplay device; and a switching element connected to said pixelelectrode via a source electrode; wherein, if C_(X) is the parasiticcapacitance between the pixel electrode and the source electrode when abad contact exists between said pixel electrode and the sourceelectrode, C_(0MAX) is the maximum value of the pixel capacitance heldby the pixel electrode when said bad contact does not exist, V_(LCMIN)is the voltage when the transmissivity at a pixel position is a minimum,and V_(LCMAX) is the voltage when the transmissivity is a maximum, acapacitance ratio RA_(C1) is set such that the following relationship isestablished:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMIN -V.sub.LCMAX).


5. 5. The display device according to claim 4, wherein, if V_(LCHL) isthe voltage when the transmissivity in said pixel position isapproximately 50% of the maximum transmissivity, the capacitance ratioRA_(C1) is set such that:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCHL /(V.sub.LCMAX -V.sub.LCHL).


6. A display device, comprising:a pixel electrode for driving thedisplay device; and a switching element connected to said pixelelectrode via a source electrode; wherein, if C_(X) is the parasiticcapacitance between the pixel electrode and the source electrode when abad contact exists between said pixel electrode and the sourceelectrode, C_(0MAX) is the maximum value of the pixel capacitance heldby the pixel electrode when said bad contact does not exist, V_(LCMIN)is the voltage when the transmissivity at a pixel position is a minimum,and V_(LCMAX) is the voltage when the transmissivity is a maximum, acapacitance ratio RA_(C2) is set such that the following relationship isestablished:

    RA.sub.C2 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMIN -V.sub.LCMAX).


7. 7. A display device, comprising:a pixel electrode for driving thedisplay device; and a switching element connected to said pixelelectrode via a source electrode;wherein, the display device includes acontact region such that it is included in either a portion of or theentire pixel electrode edge region, which is a region between one signalline connected to said switching element and a signal line adjacent tosaid one signal line, and being a region following a scan line connectedto said switching element, whereby said pixel electrode is connected tosaid source electrode in said contact region.
 8. The display deviceaccording to claim 7, wherein, if C_(X) is the parasitic capacitancebetween the pixel electrode and the source electrode when a bad contactexists between said pixel electrode, C_(0MAX) is the maximum value ofthe pixel capacitance held by the pixel electrode when said bad contactdoes not exist, V_(LCMIN) is the voltage when the transmissivity at apixel position is a minimum, and V_(LCMAX) is the voltage when thetransmissivity is a maximum, a capacitance ratio RA_(C1) is set suchthat the following relationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).


9. 9. The display device according to claim 7, wherein, if C_(X) is theparasitic capacitance between the pixel electrode and the sourceelectrode when a bad contact exists between said pixel electrode,C_(0MAX) is the maximum value of the pixel capacitance held by the pixelelectrode when said bad contact does not exist, V_(LCMIN) is the voltagewhen the transmissivity at the pixel position is a minimum, andV_(LCMAX) is the voltage when the transmissivity is a maximum, acapacitance ratio RA_(C1) is set such that the following relationship isestablished:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMIN -V.sub.LCMAX).


10. The display device according to claim 7, wherein, said contactregion includes a rectangular contact hole, a long side of which followssaid scan line, and said pixel electrode and source electrode may beconnected via said rectangular contact hole.
 11. The display deviceaccording to claim 7, wherein said contact region includes a pluralityof contact holes, the contact holes connect said pixel electrode andsaid source electrode.
 12. The display device according to claim 7,wherein a black matrix region is provided to cover either a portion ofor the entire contact region.
 13. An electronic apparatus including adisplay device according to claim
 1. 14. A method of manufacturing adisplay device that includes a pixel electrode for driving the displaydevice, and a switching element connected to said pixel electrode via asource electrode, comprising the steps of:forming said source electrode;forming an insulation film over said source electrode; forming a contactregion for connecting at least said source electrode and said pixelelectrode; and forming said pixel electrode;whereby, if C_(X) is theparasitic capacitance between the pixel electrode and the sourceelectrode when a bad contact exists between said pixel electrode and thesource electrode, C_(0MAX) is the maximum value of the pixel capacitanceheld by the pixel electrode when said bad contact does not exist,V_(LCMIN) is the voltage when the transmissivity at the pixel positionis a minimum, and V_(LCMAX) is the voltage when the transmissivity is amaximum, a capacitance ratio RA_(C1) is set such that the followingrelationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).


15. A method of manufacturing a display device that includes a pixelelectrode for driving the display device, and a switching elementconnected to said pixel electrode via a source electrode, comprising thesteps of:forming said source electrode; forming an insulation film oversaid source electrode; forming a contact region for connecting at leastsaid source electrode and said pixel electrode; and forming said pixelelectrode;whereby, if C_(X) is the parasitic capacitance between thepixel electrode and the source electrode when a bad contact existsbetween said pixel electrode and the source electrode, C_(0MAX) is themaximum value of the pixel capacitance held by the pixel electrode whensaid bad contact does not exist, V_(LCMIN) is the voltage when thetransmissivity at the pixel position is a minimum, and V_(LCMAX) is thevoltage when the transmissivity is a maximum, a capacitance ratioRA_(C1) is set such that the following relationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMIN -V.sub.LCMAX).


16. A method of manufacturing a display device that includes a pixelelectrode for driving the display device, and a switching elementconnected to said pixel electrode via a source electrode, comprising thesteps of:forming said source electrode; forming an insulation film oversaid source electrode; forming a contact region for connecting at leastsaid source electrode and said pixel electrode; and forming said pixelelectrode;whereby, the display device includes a contact region suchthat it is included in either a portion of or the entire pixel electrodeedge region, which is a region between one signal line connected to saidswitching element and a signal line adjacent to said one signal line,and being a region following a scan line connected to said switchingelement, whereby said pixel electrode is connected to said sourceelectrode in said contact region.
 17. The method according to claim 16,wherein, if C_(X) is the parasitic capacitance between the pixelelectrode and the source electrode when a bad contact exists betweensaid pixel electrode, C_(0MAX) is the maximum value of the pixelcapacitance held by the pixel electrode when said bad contact does notexist, V_(LCMIN) is the voltage when the transmissivity at the pixelposition is a minimum, and V_(LCMAX) is the voltage when thetransmissivity is a maximum, a capacitance ratio RA_(C1) is set suchthat the following relationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMAX /(V.sub.LCMIN -V.sub.LCMAX).


18. The method according to claim 16, wherein, if C_(X) is the parasiticcapacitance between the pixel electrode and the source electrode when abad contact exists between said pixel electrode, C_(0MAX) is the maximumvalue of the pixel capacitance held by the pixel electrode when said badcontact does not exist, V_(LCMIN) is the voltage when the transmissivityat the pixel position is a minimum, and V_(LCMAX) is the voltage whenthe transmissivity is a maximum, a capacitance ratio RA_(C1) is set suchthat the following relationship is established:

    RA.sub.C1 =C.sub.X /C.sub.0MAX >V.sub.LCMIN /(V.sub.LCMIN -V.sub.LCMAX).


19. The method according to claim 14, wherein, the step of forming saidcontact region includes concurrently forming the contact region forconnecting an electrode formed of the same material as the gateelectrode of said switching element and a given electrode, and thecontact region for connecting said source electrode and said pixelelectrode.